1. Technical Field
The present invention relates to an electrooptical apparatus that includes a mirror, a production method for the electrooptical apparatus, and an electronic appliance.
2. Related Art
As electronic appliances, for example, projection type display apparatuses that modulate light emitted from a light source using a plurality of mirrors (micro mirrors) of an electrooptical apparatus called DMD (digital mirror device) and perform magnifying projection of the modulated light using a projection optical system so as to display images on a screen are known. In the electrooptical apparatus used in such an electronic appliance, the mirrors are supported on torsion hinges (twist hinges) via mirror support posts and are electrically connected to the torsion hinges. Besides, the torsion hinges are supported by substrate-side bias electrodes formed on a substrate with the hinge support posts interposed therebetween, and are also electrically connected to the substrate-side bias electrodes. Therefore, by applying a bias voltage from a substrate-side bias electrode to a corresponding one of the mirrors and applying a drive voltage to an address electrode, the mirror can be driven due to electrostatic force created between the mirror and the address electrode. In a production process for an electrooptical apparatus having such a construction, torsion hinges, mirrors, and the like are formed by using a sacrificial layer made of a resin material.
If, at this time, the mirror support post of a mirror has a recess portion facing a side opposite the substrate, a large dimple is formed on the surface of the mirror, so that the reflectance of the surface of the mirror (reflecting surface thereof) decreases. Therefore, JP-T-2007-510174 proposes that an inorganic material is accumulated on surfaces of the mirror support posts, the sacrificial layer, etc., and polished, and then a reflecting film that forms the mirrors is formed. Besides, for formation of a mirror support post, JP-A-8-227042 proposes a construction in which a metal layer is formed on a surface of a columnar sacrificial layer (resin layer) left on a torsion hinge.
However, in order to fill the recess portion by accumulating an inorganic material as in a construction described in JP-T-2007-510174, the inorganic material needs to be accumulated to a considerably great thickness; moreover, the inorganic material cannot be polished at high speed. Therefore, there arises a problem that it takes a long processing time to remove the inorganic material from the surfaces of the sacrificial layer and the like by polishing.
Furthermore, if a mirror support post is formed by stacking a metal layer on a columnar resin layer as in the construction described in JP-A-8-227042, there is a risk that a gas may be produced from the sacrificial layer when the temperature of the electrooptical apparatus rises due to emitted light or due to heat generation of the substrate or the like at the time of operating a drive circuit. Such a gas, if it adheres to the surface (reflecting surface) of a mirror, degrades the reflectance of the mirror, and is therefore not preferable. Furthermore, in order to form a torsion hinge (twist hinge) and a mirror support post, it is necessary to adopt a step of forming two metal layers and of forming an insulating intermediate layer between the two metal layers and performing the patterning thereof, resulting in a complicated production process for the electrooptical apparatus.